There are various sleep devices in the market today. Some sleep devices are used in sleep labs for diagnosing sleep-related illnesses or conditions. In those applications, the sleep devices employ wet electrodes for detecting signals such as EEG (Electroencephalography), EMG (Electromyography), and EOG (Electrooculargraph), signals of a user for diagnostics. The application of wet electrodes to skin generally requires a conductive gel on the electrode to secure the attachment of the electrode to skin. These wet electrode based systems are thought to be uncomfortable and not suitable for home use, despite the fact that some wet electrodes provide better EEG signal recordings than certain other competing electrodes. In the consumer market, there are now take-home sleep devices that allow a user to monitor and/or track sleep at home. Many of these take-home sleep devices utilize accelerometers to track the physical movements of a user while asleep, e.g., the tossing and turning experienced by the user. Also available now in the consumer market is a sleep tracking device offered by Zeo Inc., which employs dry electrodes, as opposed to wet electrodes, for sensing EEG signals of a user while asleep. The application of dry electrodes to a user's skin requires a headband to secure the dry electrodes to skin.
However, the above-described sleep devices are single mode devices as each device relies on a single mechanism for receiving input signals (e.g., wet electrode, accelerometer, or dry electrode). Additionally, users prefer more choices in terms of the different ways of wearing or using a sleep device. For example, a user may prefer wearing a headband on some nights and a wristband on other nights. These single-mode devices in the market today limit a user to only one form of use (e.g., wearing a wristband, wearing a headband, etc.). While some sleep analysis devices include multiple sensor modalities, for example a combination of EEG electrodes and an accelerometer, such devices are not capable of determining which sensor modalities are actually outputting usable data and adjusting their operation accordingly. Thus, there exists a first need in the art for a multi-modal sleep device capable of adjusting its mode of operating based on a determination of which of a plurality of sensors is outputting useful data, thereby providing users flexibility in the way in which they use the device.